This invention relates to a surgical drainage device which is designed to drain fluids from a body cavity such as the pleural cavity and to maintain proper pressures within the body cavity.
It is essential for normal breathing that the space within the pleural cavity surrounding the lungs be free of liquid and be subject to a negative pressure so as to draw the lungs outwardly to fill this pleural cavity in order to permit proper breathing. Any invasion of the pleural cavity such as by lung surgery or by foreign objects which pierce the ribcage or, for example, where the patient has pleurisy, generates fluids in the pleural cavity which tend to obstruct normal breathing. It is necessary to provide a device which can remove these fluids from the pleural cavity and, at the same time, ensure that negative pressure is maintained within the pleural cavity.
Examples of one of the basic types of devices used for the above purposes are disclosed in U.S. Pat. Nos. 4,015,603; 4,261,362; 4,312,351 and 4,324,244. In this type of device an underwater seal chamber is formed at the top of the device by a wall or partition extending across a portion of the device. An underwater seal is created in the underwater seal chamber beneath the inlet to the device by liquids drained from the patient's body. The underwater seal serves as a diagnostic aid in the detection of leaks during inspiration in the pleural cavity or the drainage system. Also, it provides an additional barrier against the flow of atmospheric air from the device into the pleural cavity of the patient. Since the liquid seal does not have to be established by prefilling with water, this type of device is ideally-suited for use in emergency situations. Another important feature in this type of device is a one-way outflow valve located adjacent the outlet (which may be connected to a vacuum source or open to the atmosphere). This valve permits the escape of gases from within the device when the pressure therein is above that at the outlet but prevents the passage of atmospheric air into the device. As a result, the possibility of passage of atmospheric air or liquid from the liquid seal into the pleural cavity of the patient, of concern particularly during periods of high negative pressure in the pleural cavity, is greatly reduced.
However, a significant problem may sometimes arise with this type of device. Gases flowing from the pleural cavity of the patient through the liquid seal to the outlet may entrain relatively small amounts of the liquid in the seal and conduct it towards the one-way valve adjacent the outlet. This phenomenon tends to occur particularly when the liquid drained from the patient has a pronounced tendency to foam (e.g. blood and other proteinaceous liquids). Liquid contact with the one-way valve must be avoided since it can lead to impairment of the mechanical functioning of the valve.